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Glossary of Tyre Terms

If you come across a tyre term that you don’t know the meaning of, be sure to refer to this handy glossary of tyre-related words from Beaurepaires.

Aspect Ratio

Also known as the profile, the aspect ratio is the ratio of the height of the tyre's cross-section to its width. For example, if a tyre has an aspect ratio of 65, this means the tyre’s height is equal to 65% of its width.


This is the part of the tyre that contacts the rim on the wheel. It fits close to the two rims on the wheel to ensure that a tubeless tire holds air.


Kevlar is the registered trademark for a synthetic fibre developed in 1965.

Load Index

The load index is a number that corresponds to the maximum load in kilograms that a tyre can support when properly inflated. You can also find the maximum load supplied in pounds and kilograms moulded elsewhere on the tyre sidewall.

Pneumatic Tyres

Pneumatic tyres are comprised of a flexible material, such as rubber, with reinforcing materials such as wire.


This is the bridge between the tread and bead of a tyre.


This chemical compound, which is also known as silicon dioxide, is added to the rubber in tyres.


The tread is the raised rubber on the surface of the tyre which makes contact with the road.

Tyre Type

Tyre types define the proper use of the tyre. For example, “P” indicates a Passenger car tyre and “LT” means the tyre is for a Light Truck.

Tyre Width

This is the width of the tyre measured in millimetres from sidewall to sidewall.

Wheel Diameter

This is the width of the wheel from one end to the other.